Fluorine-vacancy (FV) complexes have been directly observed in the Si_0.94Ge_0.06 layer in a Si-SiGe-Si structure, using variable-energy positron annihilation spectroscopy (VEPAS). These complexes are linked to the significant reduction of boron diffusion in the SiGe layer via... (Read more)

In this paper we present a systematic study on the formation of He ion implantation induced nanovoids in Si and how they influence the self-interstitial (Is) supersaturation, thus affecting the diffusion and electrical activation of implanted boron in crystalline silicon. We implanted He ions... (Read more)

Positron lifetime spectroscopy was used to study native vacancy defects in semi-insulating silicon carbide. The material is shown to contain (i) vacancy clusters consisting of four to five missing atoms and (ii) Si-vacancy-related negatively charged defects. The total open volume bound to the... (Read more)

We have measured positron lifetime and Doppler broadening in highly As-doped silicon containing thermally generated V-As₃ defect complexes (vacancy is surrounded by three arsenic atoms). We observe positron detrapping from the V-As₃ defect complex and determine... (Read more)

We report the diffusion of boron, arsenic, and phosphorus in silicon isotope multilayer structures at temperatures between 850 °C and 1100 °C. The diffusion of all dopants and self-atoms at a given temperature is modeled with the same setting of all native-point-defect-related parameters.... (Read more)

The migration of monovacancies (V⁰) and self-interstitials (I) has been observed in ion-implanted low-doped float-zone silicon by variable-energy positron annihilation spectroscopy. V⁰ and I were created by the in situ implantation of ~20 keV... (Read more)

We have determined silicon self-diffusivity at temperatures 735–875 °C based on the Raman shift of longitudinal optical phonon frequencies of diffusion annealed ²⁸Si/³⁰Si isotope superlattices. The activation enthalpy of 3.6 eV is obtained in such low temperature... (Read more)

Nitrogen-doping effects in silicon crystal growth have been theoretically studied using thermodynamical simulation based on first-principles calculation results. The results show that the densities of various complexes are determined in the balance between the enthalpy effects and the entropy... (Read more)

Density-functional-theory calculations were performed for the unrelaxed +2 Si vacancy and +2 self-interstitial utilizing periodic boundary conditions and two different methods—the uniform background charge method and the local moment counter charge method—for circumventing the divergence... (Read more)

The annealing behavior of defects observed in electron paramagnetic resonance (EPR) and photoluminescence (PL) is discussed. We consider the divacancy (the P6/P7 EPR centers) and a previously unreported EPR center that we suggest is a V_C-V_Si-V_C... (Read more)

Atomic configurations, formation energies, electronic transition energies, and binding energies of the silicon divacancy in the +1, 0, −1, and −2 charge states were obtained from density functional theory calculations. The calculations were performed using the local density approximation... (Read more)

The atomic configurations and formation energies of a silicon vacancy in the +2, +1, 0, −1, and −2 charge states have been computed using density-functional theory with norm-conserving pseudopotentials and a plane wave basis. Calculations were performed in simple cubic supercells using... (Read more)

Electron paramagnetic resonance and ab initio supercell calculations suggest that the P6/P7 centers, which were previously assigned to the photoexcited triplet states of the carbon vacancy-antisite pairs in the double positive charge state, are related to the triplet ground... (Read more)

The transient enhanced diffusion of acceptor impurities severely affects the realization of ultrahigh doping regions in miniaturized Si-based devices. Fluorine codoping has been found to suppress this transient diffusion, but the mechanism underlying this effect is not understood. It has been proposed that fluorine-impurity or fluorine–native-defect interactions may be responsible. Here we clarify this mechanism combining first-principles theoretical studies of fluorine in Si and purposely designed experiments on Si structures containing boron and fluorine. The central interaction mechanism is the preferential binding of fluorine to Si-vacancy dangling bonds and the consequent formation of vacancy-fluorine complexes. The latter effectively act as traps for the excess self-interstitials that would normally cause boron transient enhanced diffusion. Instead, fluorine-boron interactions are marginal and do not play any significant role. Our results are also consistent with other observations such as native-defect trapping and bubble formation. (Read more)

We show direct evidence, obtained by positron annihilation spectroscopy, for the complexing of fluorine with vacancies in silicon. Both float zone and Czochralski silicon wafers were implanted with 30 keV fluorine ions to a fluence of 2×10¹⁴ ions/cm², and studied in the... (Read more)

We utilize spin-dependent recombination (SDR) to observe deep level trap defects at or very near the interface of 6H silicon carbide and the SiO₂ gate dielectric in SiC metal-oxide-semiconductor field effect transistors. The SDR response is strongly correlated to SiC/SiO₂... (Read more)

Process-induced defects are a serious issue for modern sub-micron Si LSIs. To characterize such defects, two different techniques are useful: electrically detected magnetic resonance (EDMR) and transmission electron microscope (TEM), which can detect small (point) and extended defects, respectively. We applied EDMR and TEM to the issue of defect-induced leakage currents in dynamic-random-access memory (DRAM) cells. For our DRAM samples (a 0.25- μm-rule series), although TEM showed no extended defects, EDMR successfully detected two types of point defects: V₂+O x (Si divacancy-oxygen complexes) and larger Si vacancies (at least larger than V₆). We confirmed that these defects are the source of DRAM leakage currents. The observed defects were formed by ion implantation processes, but were more thermally stable than those in bulk Si crystals. The origins of this enhanced stability are attributed to the presence of oxygen atoms and a strong mechanical strain in LSIs. To clarify the origin of the complicated strain in LSI structures, we can directly measure the local-strain distribution in DRAM samples by means of convergent-beam electron diffraction (CBED) using TEM, which provides us with a valuable hint for understanding the formation mechanism of process-induced defects. (Read more)

mplanted fluorine is observed to behave unusually in silicon, manifesting apparent uphill diffusion and reducing diffusion and enhancing activation of boron. In order to investigate fluorine behavior, we calculate the energy of fluorine defect structures in the framework of density functional theory. In addition to identifying the ground-state configuration and diffusion migration barrier of a single fluorine atom in silicon, a set of energetically favorable fluorine defect structures were found (F_nV_m). The decoration of vacancies and dangling silicon bonds by fluorine suggests that fluorine accumulates in vacancy-rich regions, which explains the fluorine redistribution behavior reported experimentally. (Read more)

We used electrically detected magnetic resonance to study the microscopic structure of ion-implantation-induced point defects that remained in large-scale Si integrated circuits (Si LSIs). Two types of defects were detected in the source/drain (n⁺-type) region of... (Read more)

The effect of vacancies on the behavior of F in crystalline Si has been elucidated experimentally for the first time. With positron annihilation spectroscopy and secondary ion mass spectroscopy, we find that F retards recombination between vacancies (V) and interstitials (I) because V and I trap F to form complexes. F diffuses in the V-rich region via a vacancy mechanism with an activation energy of 2.12±0.08 eV. After a long annealing time at 700ºC, F precipitates have been observed by cross-section transmission electron microscopy which are developed from the V-type defects around the implantation range and the I-type defects at the end of range. (Read more)

Ab initio plane-wave-supercell calculations are performed for the neutral monovacancies in silicon, silicon carbide and diamond using ultrasoft non-normconserving Vanderbilt pseudopotentials. We study the structure, the energetics and the single-particle energy spectrum. The local symmetry, the... (Read more)

Electron paramagnetic resonance measurements on float-zone silicon implanted with protons at ?50 K followed by heating to room temperature have revealed two signals S1_a and S1_b belonging to the S1 group of signals. S1_a and S1_b both originate from defects... (Read more)

(Read more)

EPR studies of silicon irradiated at 20.4 K and 4.2 K by 1.5 MeV and 46 MeV electrons are described. In 46 MeV irradiations the dominant defects formed appear to be divavancies and other multiple defect aggregates which liberate vacancies throughout the anneal to room temperature as they reorder, recombine, etc. For 1.5 MeV irradiations group III atoms play a vital role in p- and n-type materials in trapping interstitials and stabilizing damage. Carbon and oxygen are not effective interstitial traps at these temperatures. Evidence of limited vacancy migration during irradiation is also cited. Two distinct excited configurations of vacancy-oxygen pairs are identified as precursors to A-centre formation in n-type silicon. The kinetics for their conversion to A-centres depends strongly upon the Fermi level as does the isolated vacancy migration energy whhich is measured to be 0.18 ± 0.02 eV for the V^＝ charge state. The vacancy has four charge states, V^＋, V⁰, V^－ and V^＝. Kinetics for hole release from V^＋ reveals an activation barrier of 0.057 eV. The concentration of V^＋ at 20.4 K in boron-doped material indicates the corresponding donor level even closer to the band edge, approximately E_V ＋ 0.039 eV. Jahn-Teller energies for V⁰, V^＋, and V^－ are estimated from stress-alignment studies and confirmed to be large. Kinetics studies for reorientation from one Jahn-Teller distortion to another are also described for each charge state.